The invention relates to an auto-injector apparatus (10), comprising:a flexible container (108) containing a liquid medicant；a needle (144)communicated with the container；a housing (102), the container being received in the housing；a pump (210) disposed in the housing and positioned to engage the flexible container and expel the medicant from the container through the needle upon relative movement between the pump and the container； anda main drive spring (226) operably associated with the needle to extend the needle from a first needle position wherein the needle is completely received in the housing to a second needle position wherein the needle protrudes from the housing.The pump comprises a roller.
